The present invention relates to ladle systems for pouring molten metal. More particularly, the present invention discloses automatic ladle systems for supplying metered amounts of metal for use with die casting machines.
Die casting machines typically employ a plunger system operating within a hollow shot sleeve in the machine for forcing molten metal under high pressure into a die. After the metal cools properly a casting will be formed. For proper operation the hollow shot sleeve must be filled with a metered amount of molten metal. Excess metal which is not required to fill the casting is confined in the shot sleeve in front of the plunger and subsequently solidifies to form a short cylinder known as a "biscuit". For proper operation the shot sleeve and other die components must be subjected to the high temperature metal for minimal periods of time during each casting cycle to prevent unnecessary component deterioration.
Although molten metal may be supplied to the die casting machine manually, it is known in the art to provide automatic ladle apparatus. However, known prior art machines suffer from several disadvantages. During die casting it is necessary to pour molten metal into the shot sleeve of the die casting machine through a small pour hole provided for this purpose. Machines which are inaccurate tend to splash or waste metal. Alternatively the use of a funnel or trough for directing the molten metal may be required. Molten metal is often wasted when sudden ladle movements cause spilling or sloshing.
Conventional die casting machines require pouring in confined areas, the ladle support and pivot mechanisms in an automatic ladle system must have very little overhang. Also die casting machines usually have some form of projecting rib on each side of the center of the front platen where pouring takes place. In order to clear the structure the ladle must retract a considerable distance when moving to the pouring position. Thus it would seem beneficial to provide an automatic ladler machine with some form of means whereby the ladle may move inwardly and outwardly with respect to the apparatus as it is radially moved between filling and pouring positions.
Prior art automatic ladle systems typically misfunction in response to moderate variation in metal bath level during the filling operation. This results in an increase in labor costs since the metal holding furnace must be refilled constantly with such troublesome machines. During operation ladles require the application of a protective coating once or twice a shift in order to prevent attack or deterioration caused by the molten metal being transferred. Prior art designs usually require large amounts of down time in order to change ladles to apply a protective coating. In the prior art ladle immersion control systems have employed level detectors usually including probes which lower into molten metal. As the probes are immersed in the molten metal an electrical circuit is completed triggering a down travel stop mechanism. With construction of this type molten metal often builds up on the probe and high temperatures can destroy insulation, break wires, and otherwise injure the apparatus.